hi!
i use UPNP on my Netgear DG834G v1 with programs such Azureus & Emule Morph XT and it just works great! Never had any security problem
It'd be a very useful to get UPNP on HFS!
i use some upnp on my other file sharing programs too, but if hfs don´t do it automatically, well, i guess that there are some other prioritys on the software, like auto thumbnail creation, some server side suport like php :-p , or webadmin, i don´t know, but it is my guess....
sorry about my poor english, but i don´t know how to express myself in english as im thinking in portuguese....